Coelenteramide analogs

Abstract

There has been a need for coelenteramide analogs or the like that produce fluorescent proteins which exhibit different fluorescent characteristics from those of the existing fluorescent proteins. Disclosed is a compound represented by general formula (1) (wherein R 1 represents a substituted or unsubstituted aryl, a substituted or unsubstituted arylalkyl, a straight or branched alkyl which may optionally be substituted with an alicyclic group, an alicyclic group or a heterocyclic group; R 2 represents hydrogen or —(SO 2 )R 4 ; R 3 represents hydrogen, hydroxyl, methoxy or acetoxy; R 4 represents a substituted or unsubstituted aryl, a substituted or unsubstituted arylalkyl or a straight or branched alkyl which may optionally be substituted with an alicyclic group; and X 1 represents —C(═S)— or —SO 2 —).

The invention claimed is: 
     
       1. A compound represented by general formula (1) below: 
       
         
           
           
               
               
           
         
         wherein: 
         R 1  is a substituted or unsubstituted aryl, a substituted or unsubstituted arylalkyl, a straight or branched alkyl which may optionally be substituted with an alicyclic group, an alicyclic group or a heterocyclic group; 
         R 2  is hydrogen or —(SO 2 )R 4 ; 
         R 3  is hydrogen, hydroxy, methoxy or acetoxy; 
         R 4  is a substituted or unsubstituted aryl, a substituted or unsubstituted arylalkyl, or a straight or branched alkyl which may optionally be substituted with an alicyclic group; and, 
         X 1  is —C(═S)— or —SO 2 —. 
       
     
     
       2. The compound according to  claim 1 , wherein R 1  in the general formula (1) is phenyl, p-methylphenyl, p-hydroxyphenyl, p-methoxyphenyl, p-acetoxyphenyl, p-nitrophenyl, benzyl, α-hydroxybenzyl, 4-methylbenzyl, 4-hydroxybenzyl, 4-methoxybenzyl, 4-acetoxybenzyl, 4-nitrobenzyl, phenylethyl, methyl, ethyl, propyl, 2-methylpropyl, 2-methylpropanyl, cyclohexylmethyl, cyclohexylethyl, adamantylmethyl, cyclopentylmethyl, cyclohexyl or thiophen-2-yl. 
     
     
       3. The compound according to  claim 1 , wherein R 2  in the general formula (1) is hydrogen, benzenesulfonyl, p-toluenesulfonyl, 4-hydroxyphenylsulfonyl, 4-methoxyphenylsulfonyl, 4-acetoxyphenylsulfonyl, 4-nitrophenylsulfonyl, benzylsulfonyl, α-hydroxybenzylsulfonyl, 4-methylbenzylsulfonyl, 4-hydroxybenzylsulfonyl, 4-methoxybenzylsulfonyl, 4-acetoxybenzylsulfonyl, 4-nitrobenzylsulfonyl, phenylethylsulfonyl, methanesulfonyl, ethylsulfonyl, propylsulfonyl, 2-methylpropylsulfonyl, 2-methylpropanylsulfonyl, cyclohexylmethylsulfonyl, cyclohexylethylsulfonyl, adamantylmethylsulfonyl or cyclopentylmethylsulfonyl. 
     
     
       4. The compound according to  claim 1 , which is selected from the group consisting of the compounds described below: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
       5. The compound according to  claim 1 , which is selected from the group consisting of the compounds described below: 
       
         
           
           
               
               
           
         
       
     
     
       6. A blue fluorescent protein comprising the compound according to  claim 1 , the apoprotein of a calcium-binding photoprotein and a calcium ion or a divalent or trivalent ion substitutable for the calcium ion. 
     
     
       7. A process for producing a blue fluorescent protein, which comprises reacting the compound according to  claim 1  with the apoprotein of a calcium-binding photoprotein in the presence of a calcium ion or a divalent or trivalent ion substitutable for a calcium ion. 
     
     
       8. The process according to  claim 7 , wherein the reaction is performed in the presence of a reducing agent. 
     
     
       9. A greenish fluorescent protein comprising the compound according to  claim 1  and the apoprotein of a calcium-binding photoprotein. 
     
     
       10. A process for producing a greenish fluorescent protein, which comprises treating the blue fluorescent protein according to  claim 6  with a chelating agent for removing a calcium ion or a divalent or trivalent ion substitutable for a calcium ion. 
     
     
       11. A process for producing a calcium-binding photoprotein, which comprises reacting the greenish fluorescent protein according to  claim 9  with coelenterazine or an analog thereof. 
     
     
       12. The process according to  claim 11 , wherein the reaction of the fluorescent protein with coelenterazine or an analog thereof is performed in the presence of a reducing agent.